Various analytic and diagnostic approaches have been devised for noninvasive chemical analysis. Such approaches include, for example, near-IR spectrometry and acoustic-resonance spectrometry.
More specifically, as disclosed in copending U.S. patent application Ser. No. 945,202, filed Sep. 15, 1992 and entitled APPARATUS AND METHOD FOR ANALYZING TISSUE, (the disclosure of which is fully incorporated herein by reference), near-IR spectrometry may be utilized, for example, to determine the presence and relative concentrations of cholesterol and lipoproteins in a human blood matrix. The article "Ultrasonic Resonance Spectroscopic Analysis of Microliters of Liquids", Applied Spectroscopy, Volume 42, No. 3, 1988, pp. 526-529, describes a method of utilizing ultrasonic resonance techniques for the identification of microliters of liquids. This ultrasonic technology is also already used to sense the types and amounts of gasses in an air sample by detecting resonant frequency shifts.
Up to the date of the present invention, however, near-IR spectrometry and acoustic-resonance spectrometry have only been utilized separately and not in combination. Advantageously, the present inventor has now found that the two techniques may be utilized together in a "hyphenated" fashion to achieve a surprising, synergistic and more powerful result. Specifically, ultrasound and near-IR light may be made to interact to provide additional selectivity for targeted analytes in a sample. Further, the present inventor has found that the addition of powerful magnets adds a third dimension to the analysis by enabling detection of ultrasonically induced electrical currents in the sample. Thus, the concentration of electrolytes in a specimen or subject undergoing analysis may be determined accurately and noninvasively. This information may then be utilized to essentially eliminate near-IR spectral interference from water thereby enhancing the sensitivity and performance of this novel analytical technique.